Comments

commit cb83b629b remove the NODE sched domain and check if the node
distance in SLIT table is farther than REMOTE_DISTANCE, if so, it will
lose the load balance chance at exec/fork/wake_affine points.
But actually, even the node distance is farther than REMOTE_DISTANCE,
Modern CPUs also has QPI like connections, that make memory access is
not too slow between nodes. So above losing on NUMA machine make a
huge performance regression on benchmark: hackbench, tbench, netperf
and oltp etc.
This patch will recover the scheduler behavior to old mode on all my
Intel platforms: NHM EP/EX, WSM EP, SNB EP/EP4S, and so remove the
perfromance regressions. (all of them just has 2 kinds distance, 10 21)
Signed-off-by: Alex Shi <alex.shi@intel.com>
---
kernel/sched/core.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

On Wed, 2012-06-06 at 14:52 +0800, Alex Shi wrote:
> - if (sched_domains_numa_distance[level] > REMOTE_DISTANCE)> + if (sched_domains_numa_distance[level] > RECLAIM_DISTANCE)
I actually considered this.. I just felt a little uneasy re-purposing
the RECLAIM_DISTANCE for this, but I guess its all the same anyway. Both
mean expensive-away-distance.
So I've taken this.
thanks!
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Hello.
On 06-06-2012 10:52, Alex Shi wrote:
> commit cb83b629b
Please also specify that commit's summary in parens.
> remove the NODE sched domain and check if the node> distance in SLIT table is farther than REMOTE_DISTANCE, if so, it will> lose the load balance chance at exec/fork/wake_affine points.
> But actually, even the node distance is farther than REMOTE_DISTANCE,> Modern CPUs also has QPI like connections, that make memory access is
"Is" not needed here.
> not too slow between nodes. So above losing on NUMA machine make a> huge performance regression on benchmark: hackbench, tbench, netperf> and oltp etc.
> This patch will recover the scheduler behavior to old mode on all my> Intel platforms: NHM EP/EX, WSM EP, SNB EP/EP4S, and so remove the> perfromance regressions. (all of them just has 2 kinds distance, 10 21)
> Signed-off-by: Alex Shi<alex.shi@intel.com>
WBR, Sergei
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On 06/06/2012 05:01 PM, Peter Zijlstra wrote:
> On Wed, 2012-06-06 at 14:52 +0800, Alex Shi wrote:>> - if (sched_domains_numa_distance[level] > REMOTE_DISTANCE)>> + if (sched_domains_numa_distance[level] > RECLAIM_DISTANCE) > > I actually considered this.. I just felt a little uneasy re-purposing> the RECLAIM_DISTANCE for this, but I guess its all the same anyway. Both> mean expensive-away-distance.>
I understand you, the BIOS guys don't have a good alignment with us on
this.
> So I've taken this.> > thanks!
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